Conventional mechanisms for connecting a flap to a main wing element include flap track mechanisms, drop link mechanisms, and multi-bar linkage mechanisms.
Flap track mechanisms employ a track on which the flap runs on roller bearings as it moves between its retracted and extended positions. The advantage of a flap track mechanism is that the track can be shaped to closely control the motion of the flap. The disadvantages are that the mechanism is heavy, complex, expensive to produce, and requires a large number of roller bearings (which are prone to failure).
Drop link mechanisms employ a rigid drop link which is pivotally coupled at one end to the main wing element and to the flap at the other end. A first advantage of a drop link mechanism is that it is simple and robust. A second advantage is that the drop link can transmit lift forces efficiently from the flap to the main wing element. A disadvantage is that only simple rotational motion can be imparted to the flap.
U.S. Pat. No. 2,608,364 and U.S. Pat. No. 4,605,187 disclose various multi-bar linkage mechanisms for deploying a trailing edge flap. A first advantage of these mechanisms is that they are relatively compact when the flap is in its fully retracted position. As a result, the aerodynamic effect of the mechanism is minimal, at least when the flap is retracted. A second advantage of these mechanisms is that they allow a relatively complex path to be followed by the flap, in comparison with a drop link mechanism. A first disadvantage is that the mechanism is relatively complex compared with a drop link mechanism. A second disadvantage is that the mechanism is not able to transmit lift forces efficiently from the flap to the main wing element, resulting in an inefficient and heavy structure.